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G8MNY > TECH 29.06.05 17:53l 121 Lines 5426 Bytes #999 (0) @ WW
BID : 52038_GB7CIP
Read: GUEST OE7FMI
Subj: Petrol Generators for /P SSB 1/4
Path: DB0FHN<DB0MRW<OK0PPL<DB0RES<DK0WUE<7M3TJZ<HS1LMV<TU5EX<CX2SA<GB7YFS<
GB7CIP
Sent: 050629/0707Z @:GB7CIP.#32.GBR.EU #:52038 [Caterham] $:52038_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (Updated Jul 04)
/P POWER NEEDS
A generating set capable of handling several 400W SSB stations at once is very
uneconomical. This is because a typical constant RPM engine & alternator uses
about 30% of it's energy just to overcome the mechanical losses, cooling etc,
as well as the alternator exciting & cooling needs.
Using under rated generator sets is more economical, but obviously very prone
to regulation problems on peak load.
LOAD SHARING/conditioning
By floating a car battery on small power source very large peak power can
easily be drained for SSB work. eg 200W SSB needs 30A peak, & 10A PSU will be
able to cope with that provided is is well rated. But this is not so good for
high power FM, but the battery will still recover on Rx.
ÚÄÄÄÄÄÄÄÄÄ¿ ÚÄÄÄ¿ 13A FUSE 40A FUSE ÚÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ SMALL ÃÄÄ´PSUÃÄÄÄo\oÄÄÄÄÄÄÂÄÄÄÄÄo/oÄÄÄÄ´RIG & QRO PA³
³GENERATOR³ ÀÄÄÄÙ ÚÄÄÄÁÄÄÄ¿ ÀÄÄÄÄÄÄÄÂÄÄÄÄÙ
ÀÄÄÄÄÂÄÄÄÄÙ ³BATTERY³ _³_
_³_ ÀÄÄÄÄÄÄÄÙ ////
////
Also ensuring that no Tx station sharing a generator, has to run full carrier
power for tuning up valve PAs by using "werlos" (not whistles) & PEP METERS,
can solve excessive mains dips on heavily loaded generators enabling several
400w SSB stations to be run from a single 1.5KW generator.
FULL POWER CW/Whistle "WERLO" POWER
400W´-------- - - - MEAN 400W´ -, , - - - PEAK READING METER POWER
200W´ 200W´/' ³ / \ _ _ _ mean power
100W´ 100W´. ³ / ³ generator load!
50W´ 50W´ ³/
25W´ 25W´ ³
0 ÁÄÄÄÄÄÄÄÄ 0 ÁÄÄÄÄÄÄÄÄÄÄ
TIME TIME
eg. 400W station needs at least 800W DC I/P (class AB2) for full carrier tuning
up, but only 450W DC for spoken "werlo" 400W PEP tuning up.
MAGNETOs
Small generators having no start battery, they use magneto ignition, which is
housed in the flywheel. Powerful magnets built into the flywheel pass over a
static coil.
SPARK===, __________ IGNITION
PLUG )|( ³ ³ TIMING
)|( C === >< POINTS
MAGNETOÀÄ´ ÀÄÄÄÄÄ´
_³_ _³_
//// ////
The engine axle has a cam on it that operates a set of shorting contacts called
"points". Variable speed engines will have a movable cam, but not constant RPM
generators. These points short out the primary coil with a condenser (0.5uF
high voltage capacitor) across the points as well. The points are arranged to
open a few degrees before "Top Dead Centre", when the magnets are also across
the coil. As the points open the magnetic flux is allowed to enter the coils, &
soon produces a decaying oscillation with the condenser. A second high voltage
coil (that can be an external Ignition transformer coil), produces 15-25KV to
power the spark plug.
SPARK===, __³\³_______
PLUG )|( ³/³ +ve _³_
)|( \ /ÄÄÄÂÄÄÄÂÄÄÄÂÄÄ2KÄÄÄÄÄ¿ TIMING
MAGNETOÀÄ´ SCR ÄÂÄ === _³_ ³ +ve )³ PULSE
³ ³ 1n ³ /_\ 1K )³ PICKUP
³ ÃÄÄÄÄÁÄÄÄÁÄÄÄÙ )³ COIL
_³_ _³_ _³_
//// //// ////
Electronic types replace the points with an SCR that suddenly shorts out the
magneto +ve voltage as the magnets pass. A separate induction timing pickup
coil & small magnet on the crankshaft produce a precise turn on timing pulse,
resulting in the sudden change in the magneto primary winding voltage & the
secondary then produces the high voltage.
IGNITION QRM
On a busy band (contests) it is undesirable to use Rx noise blankers to remove
generator ignition noise, as this normally makes the larger band signals very
wide.
The ignition suppression described here should reduce QRM by > 40dB. This is
greater than can be achieved with resistive lead or resistive cap or resistive
plug together!
There are 2 causes of ignition QRM. Radiation from the lead (Aerial) &
radiation from the spark plug itself.
Suppress the lead with a large coax braid placed over the ignition lead &
earthed only at the cylinder head! This stops all radiation from the lead, but
not from the plug & cap.
For the plug cap make a metal cover to go over the plug & resistive plug cap.
Thin Copper or Tin Can is ideal as it is easily soldered (the plug should not
run that hot in service that the solder melts!). It should be shaped to be a
tight fit on the plug hexagonal, & cover the top of the plug cap. This must
made water tight as any moisture here with stop the generator starting on a
damp morning.
TIGHT FIT METAL COVER
ÄÄÄÄÄÄÄÄ¿_ _ _ _ _ _ _ _ _ _
³ÄÄÄ¿___ _ÄÄÄÄÄÄÄ¿ ³ COAX BRAID
CYLINDER³SPARK ÀÄ¿ ³ PLUG ³ ================= EHT
HEAD ³PLUG___ÚÄÙ_³ CAP ³:::::::::::::::::::::::::::::: LEAD
³ÄÄÄÙ ÄÄÄÄÄÄÄÙ Ú=================
³- - - - - - - - - - Ù ³ AS LONG AS
BOLT³0=====================Ù POSSIBLE
ÄÄÄÄÄÄÄÄÙTAG TWISTED COAX BRAID
Suppressing plugs & screened caps are also available, but resistive lead as
used on cars is not normally possible due to the magneto lead connection.
Part 2 has Oil Alarm, Economy, & Alternators.
Why Don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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